Direct Nuclear Spectroscopic Evidence against Lithium Incorporation in Aqueous Chemical Bath Deposition-Grown ZnO Nanorods

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Papageorgiou, Anastasia Ziagkova, Evagelia Taimpiri, and 7 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-8681116/v1 This work is licensed under a CC BY 4.0 License Status: Published Journal Publication published 05 Mar, 2026 Read the published version in Scientific Reports → Version 1 posted 10 You are reading this latest preprint version Abstract Achieving reliable p-type conductivity in zinc oxide (ZnO) remains a long-standing challenge, with lithium frequently proposed as a candidate acceptor dopant in solution-grown ZnO. Despite numerous reports of Li-related electrical and optical effects, direct and element-specific verification of lithium incorporation in aqueous chemical bath deposited (CBD) ZnO has remained elusive. Here, complementary nuclear ion-beam techniques, Particle-Induced Gamma-ray Emission (PIGE) and Time-of-Flight Elastic Recoil Detection Analysis (ToF-ERDA), were employed to directly probe lithium incorporation in aqueous CBD-grown ZnO nanorods synthesized over a wide range of precursor concentrations. In all samples, no lithium was detected within the experimental sensitivity of either technique, establishing an upper bound for Li incorporation below 0.01 at.%. This unambiguous absence of lithium demonstrates that Li⁺ does not act as a substitutional or interstitial dopant under aqueous CBD conditions. The results are consistent with lithium influencing the growth chemistry and defect landscape of ZnO without lattice incorporation, offering a rational explanation for Li-related effects reported in solution-grown systems. More broadly, this work clarifies the role of lithium in aqueous CBD-grown ZnO nanostructures and underscores the value of nuclear spectroscopic methods for validating light-element incorporation in oxide semiconductors. Physical sciences/Chemistry Physical sciences/Materials science Physical sciences/Nanoscience and technology ZnO nanorods Li-doping aqueous chemical bath deposition PIGE ToF-ERDA point defects p-type doping Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 1. Introduction Achieving reliable p-type doping in zinc oxide (ZnO) remains a longstanding goal in semiconductor research, driven by the prospect of creating transparent optoelectronic devices, ultraviolet (UV) light emitting diodes (LEDs) and UV lasers[ 1 ]-[ 4 ]. ZnO’s wide bandgap (~ 3.3 eV), strong exciton binding energy, and compatibility with low-cost fabrication methods, combined with its inherent multifunctional properties—such as semiconducting, piezoelectric , , pyroelectric, and antibacterial behavior—make it a uniquely versatile material. These features have enabled applications ranging from piezoelectric energy harvesters [ 5 ]-[ 6 ] and piezophototronic devices [ 7 ]-[ 8 ] to triboelectric generators [ 9 ], antibacterial coatings [ 10 ], smart textiles [ 11 ], and even templates for cellular cultures [ 12 ]. However, the realization of ZnO-based p–n junctions—essential for most active electronic and optoelectronic applications—critically depends on the ability to reproducibly engineer stable p-type conductivity. Despite extensive efforts, ZnO predominantly exhibits unintentional n-type conductivity, regardless of the growth or deposition method [ 13 ] , . This intrinsic behavior remains a controversial topic and has been attributed to a complex interplay of native point defects, including oxygen vacancies (V O ), zinc interstitials (Zn i ), and various hydrogen-related configurations (hydrogen interstitials, H i , or hydrogen substituting oxygen atoms, H O ) [ 14 ]-[ 17 ]. Among these, Zn i and hydrogen-related defects are considered the most likely sources of shallow donor states due to their low formation energies under typical synthesis conditions [ 18 ]-[ 21 ]. These donor states not only limit carrier compensation but actively counteract the introduction of acceptor dopants—making p-type conversion exceptionally challenging. For many years, lithium (Li) has been proposed as a promising p-type dopant for ZnO, owing to its small ionic radius and its ability, in theory, to substitute for Zn atoms (Li Zn ), thereby introducing shallow acceptor levels [ 22 ]-[ 24 ]. Nevertheless, a consistent and reproducible pathway to p-type ZnO via lithium doping has not yet been established [ 25 ]-[ 26 ]. Theoretical and experimental studies suggest that lithium may occupy both substitutional and interstitial sites (Li i ) —where the latter behaves as a donor, neutralizing the intended acceptor behavior. Moreover, lithium may form electrically inactive complexes, such as Li Zn –Li i or Li Zn –H, or even surface states [ 27 ] further complicating carrier dynamics. This ambiguity is compounded by the fact that nearly all reports rely on indirect methods—such as changes in optical signatures or conductivity. Among the many methods used for ZnO synthesis, chemical bath deposition (CBD) stands out for its low cost, environmental friendliness, scalability, and compatibility with standard microfabrication workflows. In this context, the addition of lithium precursor salts (e.g Lithium Nitrate, LiNO 3 , or Lithium acetate, LiCOOCH 3 ) to the CBD process has been routinely reported to induce measurable changes in electrical and optical behavior—frequently attributed to successful Li doping. In several reported cases, rectifying behavior of ZnO homojunctions and successful operation of light emitting diodes and/or photodetectors have been reported [ 6 ], [ 28 ]-[ 33 ]. However, despite these indirect signatures, direct evidence of lithium incorporation into the ZnO crystal lattice has remained elusive. In a previous study, ZnO nanorods grown by CBD in the presence of lithium precursors were investigated using a combination of X-ray diffraction (XRD), temperature-dependent photoluminescence (PL), Raman spectroscopy, and X-ray absorption fine structure (XAFS) [ 34 ]. While several Li-related effects were observed, these techniques could not provide direct, element-specific confirmation of lithium incorporation into the ZnO lattice, highlighting the limitations of conventional characterization methods for light-element detection. Despite the extensive body of work addressing lithium-related effects in ZnO grown by CBD, the fundamental question of whether lithium is actually incorporated into the ZnO lattice under aqueous CBD conditions remains unresolved. Most existing studies infer Li incorporation indirectly, based on changes in electrical, optical, or structural signatures, while direct, element-specific confirmation has been largely absent, particularly for light elements such as lithium. In this context, definitive experimental verification is essential to distinguish true dopant incorporation from secondary effects arising from growth chemistry or defect redistribution. In the present work, we address this gap by employing two complementary nuclear ion-beam techniques, Particle-Induced Gamma-ray Emission (PIGE) and Time-of-Flight Elastic Recoil Detection Analysis (ToF-ERDA), which provide direct, quantitative sensitivity to lithium at trace levels [ 35 ]-[ 42 ]. By applying these methods to a systematic series of aqueous CBD-grown ZnO nanorods prepared over a wide range of precursor concentrations, we directly assess lithium incorporation and establish stringent upper bounds on its presence within the ZnO lattice. This approach enables a clear distinction between lattice incorporation and non-incorporative effects, providing a firm experimental basis for interpreting lithium-related phenomena in solution-grown ZnO. 2. Results and Discussion To rigorously investigate the long-standing uncertainty surrounding lithium incorporation in ZnO nanostructures, we initiated our study by re-examining the exact same set of hydrothermally-grown ZnO nanorods previously analyzed in our earlier work [ 34 ], which employed extensive structural and spectroscopic techniques. Building on this foundation, we subjected these samples to the two complementary nuclear ion beam techniques—PIGE and ToF-ERDA—both capable of directly detecting lithium. The sample that was grown without any lithium during CBD served as the reference. In parallel, a new series of ZnO-nanorod samples was prepared using the same two-step hydrothermal protocol, including two growths that precisely replicated conditions from the previous study [ 34 ]. The remaining specimens were designed to broaden the dataset and to ensure that previously observed variations in the electrical response [ 33 ], [ 43 ] arise from chemistry rather than doping. Thus, we extended the range of precursor concentrations, LiNO 3 to HMTA ratios, and growth scenarios, while providing reference structures identical to those used in the ZnO homojunction devices described in Refs [ 33 ] and [ 43 ]. Prior to nuclear analysis, all new samples were characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD) to confirm morphological and structural consistency. The sample nomenclature and corresponding CBD growth conditions are summarized in Table 1 . For clarity, samples are labeled as “O/N-XX-YY-ZZ,” where “O” refers to samples from the original study [ 34 ], “N” to those from the new dataset, “XX” indicates the concentration of Zn(NO 3 ) 2 ·6H₂O, “YY” the concentration of LiNO 3 , and “ZZ” the concentration of hexamethylenetetramine (HMTA). Representative SEM images of the newly prepared samples are shown in Fig. 1 , while Fig. 2 presents the corresponding XRD patterns. The morphologies are consistent with those reported previously [ 34 ] confirming the uniform formation of ZnO nanorods across all growth conditions. The XRD data display intense (002) reflections characteristic of the hexagonal wurtzite phase, with no detectable secondary phases or diffraction peaks attributable to lithium incorporation. These findings confirm that Li addition does not alter the texture or crystalline quality of ZnO under the employed CBD conditions. Consequently, any subsequent variations in electronic or defect-related behavior can be attributed to chemical and compositional effects rather than morphological disparities. Table 1 Chemical bath deposition (CBD) growth conditions and sample nomenclature Sample Zn(NO 3 ) 2 .6H 2 O Concentration (mM) LiNO 3 Concentration (mM) HMTA Concentration (mM) Li to total precursor salt molar ratio O-40-0-40 40 0 40 0 (0:40) O-40-40-40 40 40 40 0.50 (40:80) N-40-40-40 40 40 40 0.50 (40:80) N-40-20-40 40 20 40 0.33 (20:60) O-38-2-40 38 2 40 0.05 (2:40) N-38-2-40 38 2 40 0.05 (2:40) O-36-4-40 36 4 40 0.10 (4:40) N-20-20-40 20 20 40 0.50 (20:40) N-40-40-80 40 40 80 0.50 (40:80) Following structural characterization, all samples were analyzed using ToF-ERDA and PIGE. Both methods provide absolute elemental quantification with detection limits in the sub-0.01 at % range for light elements, thereby offering the sensitivity required to resolve the long-standing ambiguity surrounding Li in ZnO. Figure 3 a depicts representative results, while Fig. 3 b shows the characteristic lithium signal obtained from a certified LiF reference sample, indicating the expected position of the Li peak. Notably, no lithium was detected in any of the samples, including those synthesized with the highest LiNO 3 concentrations. The spectra were largely the same across all specimens (not shown here for brevity), and the Li peak (Fig. 3 b) was consistently absent, regardless of the LiNO 3 concentration or the fabrication round (original or newly prepared). Depth-resolved elemental profiles clearly showed Zn, O, and minor H signals across the entire probed depth (~ 200 nm), but no Li recoil peaks (Fig. 3 c). The elemental concentrations detected in the samples are reported in atomic percent (at. %) in Table 2 and Fig. 4 . As expected, all samples contained oxygen and zinc, along with trace amounts of carbon—part of which may originate from carbon buildup during ion beam exposure—and hydrogen. Assuming a bulk density of 5.61 g/cm³ for ZnO, the reported values correspond to an approximate analysis depth of up to 200 nm. Due to experimental constraints, hydrogen concentrations are representative of a slightly shallower region, with a probing depth of approximately 150 nm (Fig. 3 c). Table 2 Elemental composition of ZnO nanorods as determined by ToF-ERDA. Sample Zn (at.%) O (at.%) H (at.%) C (at.%) O-40-0-40 45 ± 2 52 ± 3 1.4 ± 0.1 0.7 ± 0.06 O-40-40-40 46 ± 2 49 ± 3 2.0 ± 0.2 2.6 ± 0.2 N-40-40-40 40 ± 2 49 ± 2 4.0 ± 0.2 2.6 ± 0.2 N-40-20-40 40 ± 2 49 ± 2 5.6 ± 0.3 5.6 ± 0.3 O-38-2-40 45 ± 2 50 ± 2 2.5 ± 0.2 0.6 ± 0.06 N-38-2-40 37 ± 2 47 ± 2 8.6 ± 0.9 6.8 ± 1.0 O-36-4-40 46 ± 2 50 ± 3 1.8 ± 0.2 1.9 ± 0.2 N-20-20-40 40 ± 2 49 ± 2 5.2 ± 0.3 4.6 ± 0.3 N-40-40-80 40 ± 2 47 ± 2 6.1 ± 0.4 5.9 ± 0.4 Beyond the key finding that no lithium was detected, the compositional analysis in Fig. 4 and Table 2 shows that all samples, irrespective of precursor salt and HMTA ratios, are non- stoichiometric and zinc deficient. This directly supports our earlier hypothesis, based on temperature dependent photoluminescence data [ 34 ], that the observed acceptor related transitions arise from zinc vacancies rather than from lithium incorporation. Moreoever, the measured oxygen excess further corroborates our previous attribution of the yellow band (YL) emission to oxygen interstitials. As shown in [ 34 ], the YL to near band edge (NBE) ratio exhibits a strong dependence on the Li to total precursor salt molar ratio in the growth solution. Figure 5 now demonstrates that this same trend is directly reflected in the oxygen atomic percentage, establishing a clear link between Li in the CBD solution and the formation of oxygen interstitials, even in the absence of measurable Li incorporation in the lattice. Given the limited penetration depth of ToF-ERDA, one might argue that the observations described above pertain only to part of the nanorods’ length, approximately 200 nm in depth. To eliminate any remaining uncertainty regarding lithium incorporation deeper within the samples, complementary PIGE measurements were performed, leveraging the method’s higher penetration capability, increased sensitivity and elemental specificity. The characteristic gamma ray expected to be emitted from the lithium nucleus via the reaction ⁷Li(p,pγ₁–₀)⁷Li at an energy of 477.6 keV, was not observed in any of the recorded spectra. One representative spectrum is shown in Fig. 6 , properly calibrated and magnified in the region of interest. It corresponds to Sample N-40-40-80, which by all expectations should contain the highest amount of Li. In all sample the 477.6 keV peak was absent. The convergence of PIGE and ToF-ERDA therefore establishes an upper limit of Li content below 0.01 at %, while verifying the overall stoichiometric stability of the ZnO matrix. These results unambiguously demonstrate that lithium does not enter the lattice in measurable quantities, neither substitutionally nor interstitially, across any of the precursor concentrations tested. The lack of detectable Li signatures, together with the preserved Zn:O balance, indicates that Li acts solely as a chemical modifier of the growth environment rather than as an active dopant. All this led us revert back to the fundamentals of aqueous chemistry, a perspective that has often been overlooked in discussions of lithium incorporation in aqueous solution-grown ZnO. The CBD of ZnO proceeds through the well-established precipitation and dehydration of zinc hydroxide, governed by the reaction: Zn + 2 (aq) + 2 OH − (aq) ↔ Zn(OH) 2(s) → ZnO (s) + H 2 O The availability of Zn²⁺ ions is ensured by the complete dissociation of zinc nitrate in water: Zn(NO 3 ) 2(aq) → Zn + 2 (aq) + 2 NO 3 − (aq) Similarly, lithium nitrate fully dissociates to yield solvated Li⁺: LiNO 3(aq) → Li + (aq) + NO 3 − (aq) The key difference lies in the solubility and precipitation equilibria of the corresponding hydroxides. Zn(OH) 2 possesses an extremely low solubility product (Ksp = 3.5×10 − 17 ) [ 44 ], which drives its immediate precipitation upon formation. In sharp contrast, LiOH remains highly soluble in water, with a solubility of about 178 g/kg at 90°C corresponding to a saturated concentration of approximately 7.4 M [ 45 ]-[ 46 ]. This is nearly two orders of magnitude higher than the maximum 80 mM LiNO₃ used in our CBD mixtures, making co-precipitation of LiOH with Zn(OH) 2 thermodynamically implausible. This behaviour is consistent with general trends in hydroxide solubility: metals whose hydroxides have low solubilities—such as Mn, Fe, Co, Ni, Cu and Ga—are known to co-precipitate with Zn(OH)₂ and can be incorporated into ZnO under CBD conditions [ 47 ]-[ 52 ]. Lithium does not fall into this category. Beyond solubility considerations, Li⁺ exhibits a strong preference for hydration. In aqueous media it forms stable tetrahedral hydration complexes [ 53 ]-[ 54 ], typically described as Li(H 2 O) 4 + , a process energetically more favourable than incorporation into the ZnO lattice, either substitutionally or interstitially. Transient interactions between Li(H 2 O) 4 + and nascent Zn(OH) 2 clusters through short-lived hydrogen bonding may occur, but these can only perturb the crystallisation dynamics rather than produce true lattice doping. Such interactions can manifest later as modified defect populations, influencing native point defects such as oxygen interstitials, vacancies, and hydrogen complexes. This chemical interpretation is strongly supported by recent experimental findings. Apostoluk et al. [ 55 ] studied ZnO nanoparticles grown in aqueous and ethanolic media with LiOH and observed a significant enhancement in visible photoluminescence quantum yield, up to approximately 13%. Nuclear Reaction Analysis, however, failed to detect any lithium within the nanoparticles, setting an upper bound of about 0.5%. Their XRD data revealed the presence of Zn(OH) 2 secondary phases in Li-containing samples, particularly at higher LiOH concentrations. The authors concluded that the observed optical improvements stem from Li-induced changes in defect chemistry—modulation of oxygen vacancy and interstitial populations, alterations in surface states, and changes in morphology—rather than from any measurable incorporation of Li into the ZnO lattice. Taken together, the precipitation equilibria, solubility limits, hydration thermodynamics, and corroborating literature converge on a unified chemical picture: under aqueous CBD conditions, Li⁺ does not enter the ZnO lattice. Instead, it modulates the growth environment and defect formation pathways, leaving a measurable imprint on structural and optoelectronic properties without functioning as a true dopant. Finally, complementary low-frequency noise (LFN) spectroscopy of homojunction devices, reported separately in Ref. [ 43 ], provides an independent verification of this interpretation. These devices incorporated ZnO nanorods grown under identical CBD conditions to those analyzed here and in Ref [ 34 ], including samples synthesized with and without lithium nitrate as a precursor. In all cases, the nanorods served as the nominal “p-type” component of the junction, paired with an undoped ZnO nanotextured film as the “n-type” layer. The LFN analysis revealed that current fluctuations follow the signature of trap-mediated conduction and space-charge-limited behavior, consistent with carrier transport dominated by native defects rather than by intentional doping. Taken together, the electrical, structural, and compositional analyses converge on a consistent interpretation: lithium, while undetectable within the ZnO crystal lattice via nuclear spectroscopy, exerts a significant influence on defect formation and redistribution during growth. These findings underscore the need for rigorous, quantitative compositional characterization in any claim of chemical doping and call for a re-evaluation of lithium’s role in ZnO-based nanomaterials. 3. Conclusions The findings presented in this study provide definitive evidence that lithium is not incorporated into the ZnO crystal lattice as a substitutional dopant –at least- under the investigated hydrothermal CBD conditions. This conclusion, initially proposed based on indirect optical and structural studies, is now confirmed through the application of two high-sensitivity ion-beam techniques—PIGE and ToF-ERDA—which directly rule out lithium presence, even at the highest precursor concentrations. Our results demonstrate that the observed changes in ZnO nanorod properties commonly attributed to lithium doping are instead due to defect-mediated effects. Specifically, Li⁺ in the growth solution influences the concentration and distribution of native defects such as zinc vacancies (V Zn ), oxygen interstitials (O i ), and hydrogen complexes. These shifts can significantly impact carrier transport behavior, as reflected in our analysis of previously fabricated devices and preliminary low-frequency noise measurements. These findings call for renewed scrutiny of p-type behavior in Li-doped ZnO, particularly when based solely on indirect electrical measurements or other spectroscopic techniques. More broadly, this work underscores the importance of integrating direct, element-specific compositional techniques—such as PIGE and ToF-ERDA—into the study of dopant incorporation in semiconductor nanomaterials and highlights the potential of nuclear analytical techniques as arbiters in unresolved questions of materials science. Their wider adoption may enable a clearer picture and more rational design of doping strategies in future optoelectronic devices fabricated with alternative cost-efficient techniques. 4. Experimental The ZnO nanorods were synthesized via a two-step, solution-based CBD method on Si (100) substrates (Siegert Wafer). Substrate cleaning was performed using a piranha solution for 15 minutes, followed by thorough rinsing with deionized water and drying under a nitrogen stream. To form the initial seed layer, a 40 mM solution of zinc acetate dihydrate [Zn(CH 3 COO) 2 ·2H 2 O, Sigma-Aldrich] in ethanol (Carlo Erba) was spin-coated at 1000 rpm for 30 seconds and annealed at 500°C on a hotplate for 10 minutes. This spin-coating/annealing cycle was repeated ten times, following the protocol established in previous works [ 34 ], [ 56 ]. For the CBD of the nanorods, the seeded substrates were immersed face-down in an aqueous solution containing 40 mM zinc nitrate hexahydrate [Zn(NO 3 ) 2 ·6H 2 O, Sigma-Aldrich] and 40 mM hexamethylenetetramine (HMTA, Panreac). The growth solution was maintained at 87°C in a water bath, and the reaction proceeded for 2 hours. To prepare nominally Li-doped ZnO nanorods, lithium nitrate (LiNO 3 , Fisher Chemical) was introduced at varying concentrations. Detailed compositions and labeling of all samples are provided in Table 1 . The morphology of the ZnO nanorods was analyzed using field-emission scanning electron microscopy (FE-SEM; JEOL JSM-7401F), enabling high-resolution imaging of surface features and nanostructure alignment. Prior to imaging, all samples were mounted on carbon tape and examined without conductive coatings to avoid altering their native surface morphology. Crystallographic structure and phase purity were evaluated by X-ray diffraction (XRD) using a Siemens D500 diffractometer configured in the Bragg–Brentano geometry. The setup employed Cu Kα radiation (λ₁ = 1.54060 Å, λ₂ = 1.54439 Å) and a pyrolytic graphite monochromator positioned in the diffracted beam path to enhance spectral resolution. Operating conditions were maintained at 40 kV and 35 mA. Diffraction data were collected over the 2θ range of 20° to 100°, using a continuous step-scan mode with an increment of 0.03° and a dwell time of 2 seconds per step. Both the aperture and anti-scatter slits were set to 1°, ensuring high signal-to-noise across the full angular sweep. Time-of-flight elastic recoil detection analysis (ToF-ERDA) was performed with a 20 MeV ¹²⁷I beam. The beam impinged at 15° to the sample surface (grazing incidence), and recoils were collected at a 30° exit angle, a geometry that cleanly separates light recoils (Li, H, C) from the Zn/O matrix and reduces near-surface depth straggling. The sample was mounted on a four - axis precision goniometer to ensure accurate incidence/collection geometry and reproducible alignment across scans. ToF–E spectra were processed and quantified with Potku (standard stopping models and depth calibration), with count rate and dead time continuously monitored and the response cross-checked against a LiF reference. Under these conditions, the conservative 3σ MDL for Li is ≤ 0.05 at.% in the near-surface region, enabling stringent upper bounds on lithium incorporation. Particle-Induced Gamma-ray Emission (PIGE) was performed with a 3 MeV proton beam. An 80% relative-efficiency HPGe detector placed 15 cm from the target at 155° recorded the 477.6 keV line of the ⁷Li(p,p′γ)⁷Li reaction. Energy and absolute-efficiency calibrations were obtained with a ¹⁵² Eu multi-γ source; live-/dead-time and pile-up were monitored, and a blank ZnO spectrum was subtracted. Spectra were processed and quantified with the Spectrw code. A certified LiF target was measured under identical conditions to verify response and compute the Currie 3σ MDL. Under these conditions, the conservative bulk-averaged MDL for Li is ≤ 0.01 at.% (~ 100 ppm), enabling a stringent constraint on lithium content in the ZnO nanorods. Declarations Competing Interests Statement The authors declare no competing interests. Funding This work was funded by the project “DeteZnOs: Budget-friendly and sustainable-by-design UV-VIS photodetectors using chemically-produced ZnO nanostructures” in the framework of H.F.R.I call “3rd Call for H.F.R.I.’s Research Projects to Support Faculty Members & Researchers” (H.F.R.I. Project Number: 24835). Author Contribution G.P.P. performed the sample fabrication, XRD and SEM measurements, and data analysis. Z.S. and D.D.C. carried out ToF-ERDA measurements. A.Z., E.T., and A.L. performed the PIGE and ToF-ERDA measurements and contributed to data analysis. Y.G.L. conducted the chemical analysis and contributed to the manuscript results discussion and revision. C.D. contributed to the result interpretation as well as the manuscript revision. A.T. supervised the study, secured funding, and contributed to the original manuscript draft. E.M. conceived and supervised the study, developed the methodology, analyzed and interpreted the data, and wrote the original and final drafts. 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Ermeidis, S. et al. Exploring the inherent variability of economically fabricated ZnO devices towards physical unclonable functions. Micromachines 16 , 627. https://doi.org/10.3390/mi16060627 (2025). Papageorgiou, G. P. et al. Investigation of hydrothermally produced ZnO nanorods and the mechanisms of Li incorporation as a possible dopant. Micro Nano Eng. 23 , 100260. https://doi.org/10.1016/j.mne.2024.100260 (2024). Spemann, D. et al. Ion beam analysis of epitaxial ZnO:(Li, Al, Ga, Sb) thin films. Nucl. Instrum. Methods Phys. Res. B . 220 , 891–896. https://doi.org/10.1016/j.nimb.2004.01.183 (2004). Kinnunen, S., Lahtinen, M., Arstila, K. & Sajavaara, T. Hydrogen and deuterium incorporation in ZnO films grown by atomic layer deposition. Coatings 11 , 542. https://doi.org/10.3390/coatings11050542 (2021). Yang, J. et al. Low-temperature atomic layer deposition of high-k SbOx for thin film transistors. Adv. Electron. Mater. 8 , 2101334. https://doi.org/10.1002/aelm.202101334 (2022). Kinnunen, S., Sajavaara, T. & Spatial ALD of Al2O3 and ZnO using heavy water. Surf. Coat. Technol. 441 , 128456. https://doi.org/10.1016/j.surfcoat.2022.128456 (2022). Polychronopoulou, K. et al. The nanostructure, wear and corrosion performance of arc-evaporated CrBxNy nanocomposite coatings. Surf. Coat. Technol. 204 , 246–255. https://doi.org/10.1016/j.surfcoat.2009.07.009 (2009). Mateus, R. et al. Helium load on W–O coatings grown by pulsed laser deposition. Surf. Coat. Technol. 355 , 215–221. https://doi.org/10.1016/j.surfcoat.2018.02.089 (2018). Kaida, A. et al. Hydrogen interstitial in H-ion implanted ZnO bulk single crystals evaluated by elastic recoil detection analysis and electron paramagnetic resonance. Nucl. Instrum. Methods Phys. Res. B . 365 , 171–174. https://doi.org/10.1016/j.nimb.2015.07.014 (2015). Matsuda, Y. et al. Antibacterial effect of a fluoride-containing ZnO/CuO nanocomposite. Nucl. Instrum. Methods Phys. Res. B . 458 , 184–188. https://doi.org/10.1016/j.nimb.2019.06.039 (2019). Kolios, A. P. et al. Impact of Li-nitrate-induced defects on electrical conduction and 1/f noise in hydrothermally grown ZnO film/nanorod homojunctions, submitted to J. Appl. Phys. –under revisions. Reichle, R. A., McCurdy, K. G. & Hepler, L. G. Zinc hydroxide: solubility product and hydroxy-complex stability constants from 12.5–75°C. Can. J. Chem. 53 , 3841–3845. https://doi.org/10.1139/v75-556 (1975). Stephen, E. F. & Miller, P. D. Solubility of lithium hydroxide in water and vapor pressure of solutions above 220°F. J. Chem. Eng. Data . 7 , 501–505. https://doi.org/10.1021/je60015a018 (1962). Haynes, W. M. CRC handbook of chemistry and physics 96th edn (CRC, 2015). Alali, H. A. et al. Effect of Mn doping on microstructure and photocatalytic properties of ZnO nanoparticles synthesized via a hydrothermal method. Mater. Res. Express . 11 , 125005. https://doi.org/10.1088/2053-1591/ad9fd8 (2024). Qiaoping, L. et al. Hydrothermal synthesis and optical properties of Fe-doped ZnO nanorods. Ferroelectrics 564 , 59–69. https://doi.org/10.1080/00150193.2020.1761702 (2020). Meky, A. I. et al. Hydrothermal fabrication, characterization and RSM optimization of cobalt-doped zinc oxide nanoparticles for antibiotic photodegradation under visible light. Sci. Rep. 14 , 52430. https://doi.org/10.1038/s41598-024-52430-8 (2024). Al-Harbi, T. Hydrothermal synthesis and optical properties of Ni-doped ZnO hexagonal nanodiscs. J. Alloys Compd. 509 , 387–390. https://doi.org/10.1016/j.jallcom.2010.09.034 (2011). Ben Saad, L., Soltane, L. & Sediri, F. Pure and Cu-doped ZnO nanoparticles: hydrothermal synthesis, structural and optical properties. Russ J. Phys. Chem. A . 93 , 2782–2788. https://doi.org/10.1134/S0036024419130259 (2019). Young, S. J., Chiou, C. L., Liu, Y. H. & Ji, L. W. Synthesis of Ga-doped ZnO nanorods by hydrothermal method and their application to UV photodetectors. Inventions 1 , 3. https://doi.org/10.3390/inventions1010003 (2016). Mähler, J. & Persson, I. A study of the hydration of the alkali metal ions in aqueous solution. Inorg. Chem. 51 , 425–438. https://doi.org/10.1021/ic2018693 (2012). Persson, I. Hydrated metal ions in aqueous solution: how regular are their structures? Pure Appl. Chem. 82 , 1901–1917. https://doi.org/10.1351/PAC-CON-09-10-22 (2010). Apostoluk, A. et al. Improved visible emission from ZnO nanoparticles synthesized via the co-precipitation method. Materials 16 , 5400. https://doi.org/10.3390/ma16155400 (2023). Papageorgiou, G. P., Karydas, A. G., Kantarelou, V. & Makarona, E. Controlled synthesis of periodic arrays of ZnO nanostructures combining e-beam lithography and solution-based processes leveraged by micro X-ray fluorescence spectroscopy. Micro Nano Eng. 8 , 100063. https://doi.org/10.1016/j.mne.2020.100063 (2020). Additional Declarations No competing interests reported. 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Insets in (c) and (d) are the corresponding images of O-38-2-40 and O-20-20-40 from ref. [34]. Scale bars in column 1 images are 1μm (magnification: x20,000), while in all other images are 100nm [magnification for column 2: x80,000 (except for b2: x100,000); magnification for column 3: x 50,000].\u003c/p\u003e","description":"","filename":"floatimage1.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-8681116/v1/05087e286fc86cfc642aa8ee.jpeg"},{"id":101805064,"identity":"607cea97-a11b-4774-8064-74201d50e7d3","added_by":"auto","created_at":"2026-02-03 19:24:48","extension":"jpeg","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":6654752,"visible":true,"origin":"","legend":"\u003cp\u003eXRD diffraction patterns of the new set of samples. The spectra have been displaced in the vertical axis for clarity. The cyan bars denote peaks of the wurtzite phase of bulk ZnO (JCPDS no 043-0002). N-40-40-40: black line; N 38-2-40: blue line; N 20-20-40: green line; N 40-40-80: magenta line.\u003c/p\u003e","description":"","filename":"floatimage2.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-8681116/v1/a86c7bc78d78b1a3b8237965.jpeg"},{"id":101805061,"identity":"fad67e37-168b-44fa-98a4-f9046ab9c4dd","added_by":"auto","created_at":"2026-02-03 19:24:47","extension":"jpeg","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":168068,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003e(a)\u003c/strong\u003e Representative ToF-ERDA result from sample N-40-40-40, \u003cstrong\u003e(b)\u003c/strong\u003e the same result with the characteristic lines of Li and F superimposed better demonstrate the Li absence. \u003cstrong\u003e(c)\u003c/strong\u003eTypical depth profile analysis derived from 3a elemental map\u003c/p\u003e","description":"","filename":"floatimage3.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-8681116/v1/63dba686d2831d51f474c5ce.jpeg"},{"id":101881357,"identity":"f31d9993-83b2-4531-bc24-7bce8bba1959","added_by":"auto","created_at":"2026-02-04 15:11:42","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":25502,"visible":true,"origin":"","legend":"\u003cp\u003eAtomic concentrations of Zn (green bars), O (blue bars), H (yellow bars), and C (magenta bars) in ZnO nanorods extracted from ToF-ERDA measurements for all investigated samples.\u003c/p\u003e","description":"","filename":"floatimage4.png","url":"https://assets-eu.researchsquare.com/files/rs-8681116/v1/f244566d8199a885790fba90.png"},{"id":101805065,"identity":"ce541422-31f3-4946-af76-64fa4b7495b4","added_by":"auto","created_at":"2026-02-03 19:24:49","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":49947,"visible":true,"origin":"","legend":"\u003cp\u003eOxygen atomic percentage measured by ToF ERDA (black squares, pink stars and blue circles, left y axis) and the ratio YL/NBE of integrated yellow band (YL) to near band edge (NBE) emission (yellow circles, right y-axis) as a function of the Li to total precursor salt molar ratio. The YL/NBE data were extracted and reprocessed from Ref. [34] (Fig. S8d).\u003c/p\u003e","description":"","filename":"floatimage5.png","url":"https://assets-eu.researchsquare.com/files/rs-8681116/v1/cdd778ed1fe7a73032ef3248.png"},{"id":101805059,"identity":"b3f23de5-1a3a-42d4-b9cc-59a8b26f9d17","added_by":"auto","created_at":"2026-02-03 19:24:47","extension":"png","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":10679,"visible":true,"origin":"","legend":"\u003cp\u003eTypical gamma-ray spectrum from the PIGE measurements. The red line at 477.6 keV marks the absence of Lithium peak related to the ⁷Li(p,pγ₁–₀)⁷Li reaction.\u003c/p\u003e","description":"","filename":"floatimage6.png","url":"https://assets-eu.researchsquare.com/files/rs-8681116/v1/17d3dd1855833c0b41e01068.png"},{"id":104250751,"identity":"7c100d4c-1dfd-448d-b05c-7df81bc1725a","added_by":"auto","created_at":"2026-03-09 16:07:43","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":10445466,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-8681116/v1/358d7f01-de30-49c6-8cc0-c99bfd5d9413.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Direct Nuclear Spectroscopic Evidence against Lithium Incorporation in Aqueous Chemical Bath Deposition-Grown ZnO Nanorods","fulltext":[{"header":"1. Introduction","content":"\u003cp\u003eAchieving reliable p-type doping in zinc oxide (ZnO) remains a longstanding goal in semiconductor research, driven by the prospect of creating transparent optoelectronic devices, ultraviolet (UV) light emitting diodes (LEDs) and UV lasers[\u003cspan additionalcitationids=\"CR2 CR3\" citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e]-[\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e]. ZnO\u0026rsquo;s wide bandgap (~\u0026thinsp;3.3 eV), strong exciton binding energy, and compatibility with low-cost fabrication methods, combined with its inherent multifunctional properties\u0026mdash;such as semiconducting, piezoelectric\u003csup\u003e,\u003c/sup\u003e, pyroelectric, and antibacterial behavior\u0026mdash;make it a uniquely versatile material. These features have enabled applications ranging from piezoelectric energy harvesters [\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e]-[\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e] and piezophototronic devices [\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e]-[\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e] to triboelectric generators [\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e], antibacterial coatings [\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e], smart textiles [\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e], and even templates for cellular cultures [\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e]. However, the realization of ZnO-based p\u0026ndash;n junctions\u0026mdash;essential for most active electronic and optoelectronic applications\u0026mdash;critically depends on the ability to reproducibly engineer stable p-type conductivity.\u003c/p\u003e \u003cp\u003eDespite extensive efforts, ZnO predominantly exhibits unintentional n-type conductivity, regardless of the growth or deposition method [\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e]\u003csup\u003e,\u003c/sup\u003e. This intrinsic behavior remains a controversial topic and has been attributed to a complex interplay of native point defects, including oxygen vacancies (V\u003csub\u003eO\u003c/sub\u003e), zinc interstitials (Zn\u003csub\u003ei\u003c/sub\u003e), and various hydrogen-related configurations (hydrogen interstitials, H\u003csub\u003ei\u003c/sub\u003e, or hydrogen substituting oxygen atoms, H\u003csub\u003eO\u003c/sub\u003e) [\u003cspan additionalcitationids=\"CR15 CR16\" citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e]-[\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e]. Among these, Zn\u003csub\u003ei\u003c/sub\u003e and hydrogen-related defects are considered the most likely sources of shallow donor states due to their low formation energies under typical synthesis conditions [\u003cspan additionalcitationids=\"CR19 CR20\" citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e]-[\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e]. These donor states not only limit carrier compensation but actively counteract the introduction of acceptor dopants\u0026mdash;making p-type conversion exceptionally challenging.\u003c/p\u003e \u003cp\u003eFor many years, lithium (Li) has been proposed as a promising p-type dopant for ZnO, owing to its small ionic radius and its ability, in theory, to substitute for Zn atoms (Li\u003csub\u003eZn\u003c/sub\u003e), thereby introducing shallow acceptor levels [\u003cspan additionalcitationids=\"CR23\" citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e]-[\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e]. Nevertheless, a consistent and reproducible pathway to p-type ZnO via lithium doping has not yet been established [\u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e]-[\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e]. Theoretical and experimental studies suggest that lithium may occupy both substitutional and interstitial sites (Li\u003csub\u003ei\u003c/sub\u003e) \u0026mdash;where the latter behaves as a donor, neutralizing the intended acceptor behavior. Moreover, lithium may form electrically inactive complexes, such as Li\u003csub\u003eZn\u003c/sub\u003e\u0026ndash;Li\u003csub\u003ei\u003c/sub\u003e or Li\u003csub\u003eZn\u003c/sub\u003e\u0026ndash;H, or even surface states [\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e] further complicating carrier dynamics. This ambiguity is compounded by the fact that nearly all reports rely on indirect methods\u0026mdash;such as changes in optical signatures or conductivity.\u003c/p\u003e \u003cp\u003eAmong the many methods used for ZnO synthesis, chemical bath deposition (CBD) stands out for its low cost, environmental friendliness, scalability, and compatibility with standard microfabrication workflows. In this context, the addition of lithium precursor salts (e.g Lithium Nitrate, LiNO\u003csub\u003e3\u003c/sub\u003e, or Lithium acetate, LiCOOCH\u003csub\u003e3\u003c/sub\u003e) to the CBD process has been routinely reported to induce measurable changes in electrical and optical behavior\u0026mdash;frequently attributed to successful Li doping. In several reported cases, rectifying behavior of ZnO homojunctions and successful operation of light emitting diodes and/or photodetectors have been reported [\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e], [\u003cspan additionalcitationids=\"CR29 CR30 CR31 CR32\" citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e]-[\u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e33\u003c/span\u003e]. However, despite these indirect signatures, direct evidence of lithium incorporation into the ZnO crystal lattice has remained elusive.\u003c/p\u003e \u003cp\u003eIn a previous study, ZnO nanorods grown by CBD in the presence of lithium precursors were investigated using a combination of X-ray diffraction (XRD), temperature-dependent photoluminescence (PL), Raman spectroscopy, and X-ray absorption fine structure (XAFS) [\u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e34\u003c/span\u003e]. While several Li-related effects were observed, these techniques could not provide direct, element-specific confirmation of lithium incorporation into the ZnO lattice, highlighting the limitations of conventional characterization methods for light-element detection.\u003c/p\u003e \u003cp\u003eDespite the extensive body of work addressing lithium-related effects in ZnO grown by CBD, the fundamental question of whether lithium is actually incorporated into the ZnO lattice under aqueous CBD conditions remains unresolved. Most existing studies infer Li incorporation indirectly, based on changes in electrical, optical, or structural signatures, while direct, element-specific confirmation has been largely absent, particularly for light elements such as lithium. In this context, definitive experimental verification is essential to distinguish true dopant incorporation from secondary effects arising from growth chemistry or defect redistribution. In the present work, we address this gap by employing two complementary nuclear ion-beam techniques, Particle-Induced Gamma-ray Emission (PIGE) and Time-of-Flight Elastic Recoil Detection Analysis (ToF-ERDA), which provide direct, quantitative sensitivity to lithium at trace levels [\u003cspan additionalcitationids=\"CR36 CR37 CR38 CR39 CR40 CR41\" citationid=\"CR35\" class=\"CitationRef\"\u003e35\u003c/span\u003e]-[\u003cspan citationid=\"CR42\" class=\"CitationRef\"\u003e42\u003c/span\u003e]. By applying these methods to a systematic series of aqueous CBD-grown ZnO nanorods prepared over a wide range of precursor concentrations, we directly assess lithium incorporation and establish stringent upper bounds on its presence within the ZnO lattice. This approach enables a clear distinction between lattice incorporation and non-incorporative effects, providing a firm experimental basis for interpreting lithium-related phenomena in solution-grown ZnO.\u003c/p\u003e"},{"header":"2. Results and Discussion","content":"\u003cp\u003eTo rigorously investigate the long-standing uncertainty surrounding lithium incorporation in ZnO nanostructures, we initiated our study by re-examining the exact same set of hydrothermally-grown ZnO nanorods previously analyzed in our earlier work [\u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e34\u003c/span\u003e], which employed extensive structural and spectroscopic techniques. Building on this foundation, we subjected these samples to the two complementary nuclear ion beam techniques\u0026mdash;PIGE and ToF-ERDA\u0026mdash;both capable of directly detecting lithium. The sample that was grown without any lithium during CBD served as the reference.\u003c/p\u003e \u003cp\u003eIn parallel, a new series of ZnO-nanorod samples was prepared using the same two-step hydrothermal protocol, including two growths that precisely replicated conditions from the previous study [\u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e34\u003c/span\u003e]. The remaining specimens were designed to broaden the dataset and to ensure that previously observed variations in the electrical response [\u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e33\u003c/span\u003e], [\u003cspan citationid=\"CR43\" class=\"CitationRef\"\u003e43\u003c/span\u003e] arise from chemistry rather than doping. Thus, we extended the range of precursor concentrations, LiNO\u003csub\u003e3\u003c/sub\u003e to HMTA ratios, and growth scenarios, while providing reference structures identical to those used in the ZnO homojunction devices described in Refs [\u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e33\u003c/span\u003e] and [\u003cspan citationid=\"CR43\" class=\"CitationRef\"\u003e43\u003c/span\u003e]. Prior to nuclear analysis, all new samples were characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD) to confirm morphological and structural consistency. The sample nomenclature and corresponding CBD growth conditions are summarized in Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e. For clarity, samples are labeled as \u0026ldquo;O/N-XX-YY-ZZ,\u0026rdquo; where \u0026ldquo;O\u0026rdquo; refers to samples from the original study [\u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e34\u003c/span\u003e], \u0026ldquo;N\u0026rdquo; to those from the new dataset, \u0026ldquo;XX\u0026rdquo; indicates the concentration of Zn(NO\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e2\u003c/sub\u003e\u0026middot;6H₂O, \u0026ldquo;YY\u0026rdquo; the concentration of LiNO\u003csub\u003e3\u003c/sub\u003e, and \u0026ldquo;ZZ\u0026rdquo; the concentration of hexamethylenetetramine (HMTA).\u003c/p\u003e \u003cp\u003eRepresentative SEM images of the newly prepared samples are shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e, while Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e presents the corresponding XRD patterns. The morphologies are consistent with those reported previously [\u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e34\u003c/span\u003e] confirming the uniform formation of ZnO nanorods across all growth conditions. The XRD data display intense (002) reflections characteristic of the hexagonal wurtzite phase, with no detectable secondary phases or diffraction peaks attributable to lithium incorporation. These findings confirm that Li addition does not alter the texture or crystalline quality of ZnO under the employed CBD conditions. Consequently, any subsequent variations in electronic or defect-related behavior can be attributed to chemical and compositional effects rather than morphological disparities.\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab1\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eChemical bath deposition (CBD) growth conditions and sample nomenclature\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"5\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eSample\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eZn(NO\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e2\u003c/sub\u003e.6H\u003csub\u003e2\u003c/sub\u003eO Concentration (mM)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eLiNO\u003csub\u003e3\u003c/sub\u003e\u003c/p\u003e \u003cp\u003eConcentration (mM)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eHMTA\u003c/p\u003e \u003cp\u003eConcentration (mM)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eLi to total precursor salt molar ratio\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eO-40-0-40\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e40\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e40\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0 (0:40)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eO-40-40-40\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e40\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e40\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e40\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.50 (40:80)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eN-40-40-40\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e40\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e40\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e40\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.50 (40:80)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eN-40-20-40\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e40\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e20\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e40\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.33 (20:60)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eO-38-2-40\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e38\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e40\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.05 (2:40)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eN-38-2-40\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e38\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e40\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.05 (2:40)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eO-36-4-40\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e36\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e40\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.10 (4:40)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eN-20-20-40\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e20\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e20\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e40\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.50 (20:40)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eN-40-40-80\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e40\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e40\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e80\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.50 (40:80)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eFollowing structural characterization, all samples were analyzed using ToF-ERDA and PIGE. Both methods provide absolute elemental quantification with detection limits in the sub-0.01 at % range for light elements, thereby offering the sensitivity required to resolve the long-standing ambiguity surrounding Li in ZnO. Figure\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003ea depicts representative results, while Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003eb shows the characteristic lithium signal obtained from a certified LiF reference sample, indicating the expected position of the Li peak. Notably, no lithium was detected in any of the samples, including those synthesized with the highest LiNO\u003csub\u003e3\u003c/sub\u003e concentrations. The spectra were largely the same across all specimens (not shown here for brevity), and the Li peak (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003eb) was consistently absent, regardless of the LiNO\u003csub\u003e3\u003c/sub\u003e concentration or the fabrication round (original or newly prepared). Depth-resolved elemental profiles clearly showed Zn, O, and minor H signals across the entire probed depth (~\u0026thinsp;200 nm), but no Li recoil peaks (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003ec).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eThe elemental concentrations detected in the samples are reported in atomic percent (at. %) in Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e and Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e4\u003c/span\u003e.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eAs expected, all samples contained oxygen and zinc, along with trace amounts of carbon\u0026mdash;part of which may originate from carbon buildup during ion beam exposure\u0026mdash;and hydrogen. Assuming a bulk density of 5.61 g/cm\u0026sup3; for ZnO, the reported values correspond to an approximate analysis depth of up to 200 nm. Due to experimental constraints, hydrogen concentrations are representative of a slightly shallower region, with a probing depth of approximately 150 nm (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003ec).\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab2\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 2\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eElemental composition of ZnO nanorods as determined by ToF-ERDA.\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"5\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\"\u0026plusmn;\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\"\u0026plusmn;\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\"\u0026plusmn;\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\"\u0026plusmn;\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eSample\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eZn (at.%)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eO (at.%)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eH (at.%)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eC (at.%)\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eO-40-0-40\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e \u003cp\u003e45\u0026thinsp;\u0026plusmn;\u0026thinsp;2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e \u003cp\u003e52\u0026thinsp;\u0026plusmn;\u0026thinsp;3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c4\"\u003e \u003cp\u003e1.4\u0026thinsp;\u0026plusmn;\u0026thinsp;0.1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c5\"\u003e \u003cp\u003e0.7\u0026thinsp;\u0026plusmn;\u0026thinsp;0.06\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eO-40-40-40\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e \u003cp\u003e46\u0026thinsp;\u0026plusmn;\u0026thinsp;2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e \u003cp\u003e49\u0026thinsp;\u0026plusmn;\u0026thinsp;3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c4\"\u003e \u003cp\u003e2.0\u0026thinsp;\u0026plusmn;\u0026thinsp;0.2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c5\"\u003e \u003cp\u003e2.6\u0026thinsp;\u0026plusmn;\u0026thinsp;0.2\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eN-40-40-40\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e \u003cp\u003e40\u0026thinsp;\u0026plusmn;\u0026thinsp;2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e \u003cp\u003e49\u0026thinsp;\u0026plusmn;\u0026thinsp;2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c4\"\u003e \u003cp\u003e4.0\u0026thinsp;\u0026plusmn;\u0026thinsp;0.2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c5\"\u003e \u003cp\u003e2.6\u0026thinsp;\u0026plusmn;\u0026thinsp;0.2\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eN-40-20-40\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e \u003cp\u003e40\u0026thinsp;\u0026plusmn;\u0026thinsp;2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e \u003cp\u003e49\u0026thinsp;\u0026plusmn;\u0026thinsp;2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c4\"\u003e \u003cp\u003e5.6\u0026thinsp;\u0026plusmn;\u0026thinsp;0.3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c5\"\u003e \u003cp\u003e5.6\u0026thinsp;\u0026plusmn;\u0026thinsp;0.3\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eO-38-2-40\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e \u003cp\u003e45\u0026thinsp;\u0026plusmn;\u0026thinsp;2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e \u003cp\u003e50\u0026thinsp;\u0026plusmn;\u0026thinsp;2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c4\"\u003e \u003cp\u003e2.5\u0026thinsp;\u0026plusmn;\u0026thinsp;0.2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c5\"\u003e \u003cp\u003e0.6\u0026thinsp;\u0026plusmn;\u0026thinsp;0.06\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eN-38-2-40\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e \u003cp\u003e37\u0026thinsp;\u0026plusmn;\u0026thinsp;2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e \u003cp\u003e47\u0026thinsp;\u0026plusmn;\u0026thinsp;2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c4\"\u003e \u003cp\u003e8.6\u0026thinsp;\u0026plusmn;\u0026thinsp;0.9\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c5\"\u003e \u003cp\u003e6.8\u0026thinsp;\u0026plusmn;\u0026thinsp;1.0\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eO-36-4-40\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e \u003cp\u003e46\u0026thinsp;\u0026plusmn;\u0026thinsp;2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e \u003cp\u003e50\u0026thinsp;\u0026plusmn;\u0026thinsp;3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c4\"\u003e \u003cp\u003e1.8\u0026thinsp;\u0026plusmn;\u0026thinsp;0.2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c5\"\u003e \u003cp\u003e1.9\u0026thinsp;\u0026plusmn;\u0026thinsp;0.2\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eN-20-20-40\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e \u003cp\u003e40\u0026thinsp;\u0026plusmn;\u0026thinsp;2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e \u003cp\u003e49\u0026thinsp;\u0026plusmn;\u0026thinsp;2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c4\"\u003e \u003cp\u003e5.2\u0026thinsp;\u0026plusmn;\u0026thinsp;0.3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c5\"\u003e \u003cp\u003e4.6\u0026thinsp;\u0026plusmn;\u0026thinsp;0.3\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eN-40-40-80\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e \u003cp\u003e40\u0026thinsp;\u0026plusmn;\u0026thinsp;2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e \u003cp\u003e47\u0026thinsp;\u0026plusmn;\u0026thinsp;2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c4\"\u003e \u003cp\u003e6.1\u0026thinsp;\u0026plusmn;\u0026thinsp;0.4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c5\"\u003e \u003cp\u003e5.9\u0026thinsp;\u0026plusmn;\u0026thinsp;0.4\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eBeyond the key finding that no lithium was detected, the compositional analysis in Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e4\u003c/span\u003e and Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e shows that all samples, irrespective of precursor salt and HMTA ratios, are non- stoichiometric and zinc deficient. This directly supports our earlier hypothesis, based on temperature dependent photoluminescence data [\u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e34\u003c/span\u003e], that the observed acceptor related transitions arise from zinc vacancies rather than from lithium incorporation.\u003c/p\u003e \u003cp\u003eMoreoever, the measured oxygen excess further corroborates our previous attribution of the yellow band (YL) emission to oxygen interstitials. As shown in [\u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e34\u003c/span\u003e], the YL to near band edge (NBE) ratio exhibits a strong dependence on the Li to total precursor salt molar ratio in the growth solution. Figure\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e5\u003c/span\u003e now demonstrates that this same trend is directly reflected in the oxygen atomic percentage, establishing a clear link between Li in the CBD solution and the formation of oxygen interstitials, even in the absence of measurable Li incorporation in the lattice.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eGiven the limited penetration depth of ToF-ERDA, one might argue that the observations described above pertain only to part of the nanorods\u0026rsquo; length, approximately 200 nm in depth. To eliminate any remaining uncertainty regarding lithium incorporation deeper within the samples, complementary PIGE measurements were performed, leveraging the method\u0026rsquo;s higher penetration capability, increased sensitivity and elemental specificity. The characteristic gamma ray expected to be emitted from the lithium nucleus via the reaction ⁷Li(p,pγ₁\u0026ndash;₀)⁷Li at an energy of 477.6 keV, was not observed in any of the recorded spectra. One representative spectrum is shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e6\u003c/span\u003e, properly calibrated and magnified in the region of interest. It corresponds to Sample N-40-40-80, which by all expectations should contain the highest amount of Li. In all sample the 477.6 keV peak was absent.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eThe convergence of PIGE and ToF-ERDA therefore establishes an upper limit of Li content below 0.01 at %, while verifying the overall stoichiometric stability of the ZnO matrix. These results unambiguously demonstrate that lithium does not enter the lattice in measurable quantities, neither substitutionally nor interstitially, across any of the precursor concentrations tested. The lack of detectable Li signatures, together with the preserved Zn:O balance, indicates that Li acts solely as a \u003cem\u003echemical modifier of the growth environment rather than as an active dopant.\u003c/em\u003e\u003c/p\u003e \u003cp\u003eAll this led us revert back to the fundamentals of aqueous chemistry, a perspective that has often been overlooked in discussions of lithium incorporation in aqueous solution-grown ZnO. The CBD of ZnO proceeds through the well-established precipitation and dehydration of zinc hydroxide, governed by the reaction:\u003c/p\u003e \u003cp\u003eZn\u003csup\u003e+\u0026thinsp;2\u003c/sup\u003e\u003csub\u003e(aq)\u003c/sub\u003e\u0026thinsp;+\u0026thinsp;2 OH\u003csup\u003e\u0026minus;\u003c/sup\u003e\u003csub\u003e(aq)\u003c/sub\u003e \u0026harr; Zn(OH)\u003csub\u003e2(s)\u003c/sub\u003e \u0026rarr; ZnO\u003csub\u003e(s)\u003c/sub\u003e + H\u003csub\u003e2\u003c/sub\u003eO\u003c/p\u003e \u003cp\u003eThe availability of Zn\u0026sup2;⁺ ions is ensured by the complete dissociation of zinc nitrate in water:\u003c/p\u003e \u003cp\u003eZn(NO\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e2(aq)\u003c/sub\u003e \u0026rarr; Zn\u003csup\u003e+\u0026thinsp;2\u003c/sup\u003e\u003csub\u003e(aq)\u003c/sub\u003e\u0026thinsp;+\u0026thinsp;2 NO\u003csub\u003e3\u003c/sub\u003e\u003csup\u003e\u0026minus;\u003c/sup\u003e\u003csub\u003e(aq)\u003c/sub\u003e\u003c/p\u003e \u003cp\u003eSimilarly, lithium nitrate fully dissociates to yield solvated Li⁺:\u003c/p\u003e \u003cp\u003eLiNO\u003csub\u003e3(aq)\u003c/sub\u003e \u0026rarr; Li\u003csup\u003e+\u003c/sup\u003e\u003csub\u003e(aq)\u003c/sub\u003e + NO\u003csub\u003e3\u003c/sub\u003e\u003csup\u003e\u0026minus;\u003c/sup\u003e\u003csub\u003e(aq)\u003c/sub\u003e\u003c/p\u003e \u003cp\u003eThe key difference lies in the solubility and precipitation equilibria of the corresponding hydroxides. Zn(OH)\u003csub\u003e2\u003c/sub\u003e possesses an extremely low solubility product (Ksp\u0026thinsp;=\u0026thinsp;3.5\u0026times;10\u003csup\u003e\u0026minus;\u0026thinsp;17\u003c/sup\u003e) [\u003cspan citationid=\"CR44\" class=\"CitationRef\"\u003e44\u003c/span\u003e], which drives its immediate precipitation upon formation. In sharp contrast, LiOH remains highly soluble in water, with a solubility of about 178 g/kg at 90\u0026deg;C corresponding to a saturated concentration of approximately 7.4 M [\u003cspan citationid=\"CR45\" class=\"CitationRef\"\u003e45\u003c/span\u003e]-[\u003cspan citationid=\"CR46\" class=\"CitationRef\"\u003e46\u003c/span\u003e]. This is nearly two orders of magnitude higher than the maximum 80 mM LiNO₃ used in our CBD mixtures, making co-precipitation of LiOH with Zn(OH)\u003csub\u003e2\u003c/sub\u003e thermodynamically implausible. This behaviour is consistent with general trends in hydroxide solubility: metals whose hydroxides have low solubilities\u0026mdash;such as Mn, Fe, Co, Ni, Cu and Ga\u0026mdash;are known to co-precipitate with Zn(OH)₂ and can be incorporated into ZnO under CBD conditions [\u003cspan additionalcitationids=\"CR48 CR49 CR50 CR51\" citationid=\"CR47\" class=\"CitationRef\"\u003e47\u003c/span\u003e]-[\u003cspan citationid=\"CR52\" class=\"CitationRef\"\u003e52\u003c/span\u003e]. Lithium does not fall into this category.\u003c/p\u003e \u003cp\u003eBeyond solubility considerations, Li⁺ exhibits a strong preference for hydration. In aqueous media it forms stable tetrahedral hydration complexes [\u003cspan citationid=\"CR53\" class=\"CitationRef\"\u003e53\u003c/span\u003e]-[\u003cspan citationid=\"CR54\" class=\"CitationRef\"\u003e54\u003c/span\u003e], typically described as Li(H\u003csub\u003e2\u003c/sub\u003eO)\u003csub\u003e4\u003c/sub\u003e\u003csup\u003e+\u003c/sup\u003e, a process energetically more favourable than incorporation into the ZnO lattice, either substitutionally or interstitially. Transient interactions between Li(H\u003csub\u003e2\u003c/sub\u003eO)\u003csub\u003e4\u003c/sub\u003e\u003csup\u003e+\u003c/sup\u003e and nascent Zn(OH)\u003csub\u003e2\u003c/sub\u003e clusters through short-lived hydrogen bonding may occur, but these can only perturb the crystallisation dynamics rather than produce true lattice doping. Such interactions can manifest later as modified defect populations, influencing native point defects such as oxygen interstitials, vacancies, and hydrogen complexes.\u003c/p\u003e \u003cp\u003eThis chemical interpretation is strongly supported by recent experimental findings. Apostoluk et al. [\u003cspan citationid=\"CR55\" class=\"CitationRef\"\u003e55\u003c/span\u003e] studied ZnO nanoparticles grown in aqueous and ethanolic media with LiOH and observed a significant enhancement in visible photoluminescence quantum yield, up to approximately 13%. Nuclear Reaction Analysis, however, failed to detect any lithium within the nanoparticles, setting an upper bound of about 0.5%. Their XRD data revealed the presence of Zn(OH)\u003csub\u003e2\u003c/sub\u003e secondary phases in Li-containing samples, particularly at higher LiOH concentrations. The authors concluded that the observed optical improvements stem from Li-induced changes in defect chemistry\u0026mdash;modulation of oxygen vacancy and interstitial populations, alterations in surface states, and changes in morphology\u0026mdash;rather than from any measurable incorporation of Li into the ZnO lattice.\u003c/p\u003e \u003cp\u003eTaken together, the precipitation equilibria, solubility limits, hydration thermodynamics, and corroborating literature converge on a unified chemical picture: under aqueous CBD conditions, Li⁺ does not enter the ZnO lattice. Instead, it modulates the growth environment and defect formation pathways, leaving a measurable imprint on structural and optoelectronic properties without functioning as a true dopant.\u003c/p\u003e \u003cp\u003eFinally, complementary low-frequency noise (LFN) spectroscopy of homojunction devices, reported separately in Ref. [\u003cspan citationid=\"CR43\" class=\"CitationRef\"\u003e43\u003c/span\u003e], provides an independent verification of this interpretation. These devices incorporated ZnO nanorods grown under identical CBD conditions to those analyzed here and in Ref [\u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e34\u003c/span\u003e], including samples synthesized with and without lithium nitrate as a precursor. In all cases, the nanorods served as the nominal \u0026ldquo;p-type\u0026rdquo; component of the junction, paired with an undoped ZnO nanotextured film as the \u0026ldquo;n-type\u0026rdquo; layer. The LFN analysis revealed that current fluctuations follow the signature of trap-mediated conduction and space-charge-limited behavior, consistent with carrier transport dominated by native defects rather than by intentional doping.\u003c/p\u003e \u003cp\u003eTaken together, the electrical, structural, and compositional analyses converge on a consistent interpretation: lithium, while undetectable within the ZnO crystal lattice via nuclear spectroscopy, exerts a significant influence on defect formation and redistribution during growth. These findings underscore the need for rigorous, quantitative compositional characterization in any claim of chemical doping and call for a re-evaluation of lithium\u0026rsquo;s role in ZnO-based nanomaterials.\u003c/p\u003e"},{"header":"3. Conclusions","content":"\u003cp\u003eThe findings presented in this study provide definitive evidence that lithium is not incorporated into the ZnO crystal lattice as a substitutional dopant \u0026ndash;at least- under the investigated hydrothermal CBD conditions. This conclusion, initially proposed based on indirect optical and structural studies, is now confirmed through the application of two high-sensitivity ion-beam techniques\u0026mdash;PIGE and ToF-ERDA\u0026mdash;which directly rule out lithium presence, even at the highest precursor concentrations.\u003c/p\u003e \u003cp\u003eOur results demonstrate that the observed changes in ZnO nanorod properties commonly attributed to lithium doping are instead due to defect-mediated effects. Specifically, Li⁺ in the growth solution influences the concentration and distribution of native defects such as zinc vacancies (V\u003csub\u003eZn\u003c/sub\u003e), oxygen interstitials (O\u003csub\u003ei\u003c/sub\u003e), and hydrogen complexes. These shifts can significantly impact carrier transport behavior, as reflected in our analysis of previously fabricated devices and preliminary low-frequency noise measurements.\u003c/p\u003e \u003cp\u003eThese findings call for renewed scrutiny of p-type behavior in Li-doped ZnO, particularly when based solely on indirect electrical measurements or other spectroscopic techniques. More broadly, this work underscores the importance of integrating direct, element-specific compositional techniques\u0026mdash;such as PIGE and ToF-ERDA\u0026mdash;into the study of dopant incorporation in semiconductor nanomaterials and highlights the potential of nuclear analytical techniques as arbiters in unresolved questions of materials science. Their wider adoption may enable a clearer picture and more rational design of doping strategies in future optoelectronic devices fabricated with alternative cost-efficient techniques.\u003c/p\u003e"},{"header":"4. Experimental","content":"\u003cp\u003eThe ZnO nanorods were synthesized via a two-step, solution-based CBD method on Si (100) substrates (Siegert Wafer). Substrate cleaning was performed using a piranha solution for 15 minutes, followed by thorough rinsing with deionized water and drying under a nitrogen stream.\u003c/p\u003e \u003cp\u003eTo form the initial seed layer, a 40 mM solution of zinc acetate dihydrate [Zn(CH\u003csub\u003e3\u003c/sub\u003eCOO)\u003csub\u003e2\u003c/sub\u003e\u0026middot;2H\u003csub\u003e2\u003c/sub\u003eO, Sigma-Aldrich] in ethanol (Carlo Erba) was spin-coated at 1000 rpm for 30 seconds and annealed at 500\u0026deg;C on a hotplate for 10 minutes. This spin-coating/annealing cycle was repeated ten times, following the protocol established in previous works [\u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e34\u003c/span\u003e], [\u003cspan citationid=\"CR56\" class=\"CitationRef\"\u003e56\u003c/span\u003e]. For the CBD of the nanorods, the seeded substrates were immersed face-down in an aqueous solution containing 40 mM zinc nitrate hexahydrate [Zn(NO\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e2\u003c/sub\u003e\u0026middot;6H\u003csub\u003e2\u003c/sub\u003eO, Sigma-Aldrich] and 40 mM hexamethylenetetramine (HMTA, Panreac). The growth solution was maintained at 87\u0026deg;C in a water bath, and the reaction proceeded for 2 hours. To prepare nominally Li-doped ZnO nanorods, lithium nitrate (LiNO\u003csub\u003e3\u003c/sub\u003e, Fisher Chemical) was introduced at varying concentrations. Detailed compositions and labeling of all samples are provided in Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e.\u003c/p\u003e \u003cp\u003eThe morphology of the ZnO nanorods was analyzed using field-emission scanning electron microscopy (FE-SEM; JEOL JSM-7401F), enabling high-resolution imaging of surface features and nanostructure alignment. Prior to imaging, all samples were mounted on carbon tape and examined without conductive coatings to avoid altering their native surface morphology.\u003c/p\u003e \u003cp\u003eCrystallographic structure and phase purity were evaluated by X-ray diffraction (XRD) using a Siemens D500 diffractometer configured in the Bragg\u0026ndash;Brentano geometry. The setup employed Cu Kα radiation (λ₁ = 1.54060 \u0026Aring;, λ₂ = 1.54439 \u0026Aring;) and a pyrolytic graphite monochromator positioned in the diffracted beam path to enhance spectral resolution. Operating conditions were maintained at 40 kV and 35 mA. Diffraction data were collected over the 2θ range of 20\u0026deg; to 100\u0026deg;, using a continuous step-scan mode with an increment of 0.03\u0026deg; and a dwell time of 2 seconds per step. Both the aperture and anti-scatter slits were set to 1\u0026deg;, ensuring high signal-to-noise across the full angular sweep.\u003c/p\u003e \u003cp\u003eTime-of-flight elastic recoil detection analysis (ToF-ERDA) was performed with a 20 MeV \u0026sup1;\u0026sup2;⁷I beam. The beam impinged at 15\u0026deg; to the sample surface (grazing incidence), and recoils were collected at a 30\u0026deg; exit angle, a geometry that cleanly separates light recoils (Li, H, C) from the Zn/O matrix and reduces near-surface depth straggling. The sample was mounted on a four\u003cb\u003e-\u003c/b\u003eaxis precision goniometer to ensure accurate incidence/collection geometry and reproducible alignment across scans. ToF\u0026ndash;E spectra were processed and quantified with Potku (standard stopping models and depth calibration), with count rate and dead time continuously monitored and the response cross-checked against a LiF reference. Under these conditions, the conservative 3σ MDL for Li is \u0026le;\u0026thinsp;0.05 at.% in the near-surface region, enabling stringent upper bounds on lithium incorporation.\u003c/p\u003e \u003cp\u003eParticle-Induced Gamma-ray Emission (PIGE) was performed with a 3 MeV proton beam. An 80% relative-efficiency HPGe detector placed 15 cm from the target at 155\u0026deg; recorded the 477.6 keV line of the ⁷Li(p,p\u0026prime;γ)⁷Li reaction. Energy and absolute-efficiency calibrations were obtained with a \u003cb\u003e\u0026sup1;⁵\u0026sup2;\u003c/b\u003eEu multi-γ source; live-/dead-time and pile-up were monitored, and a blank ZnO spectrum was subtracted. Spectra were processed and quantified with the Spectrw code. A certified LiF target was measured under identical conditions to verify response and compute the Currie 3σ MDL. Under these conditions, the conservative bulk-averaged MDL for Li is \u0026le;\u0026thinsp;0.01 at.% (~\u0026thinsp;100 ppm), enabling a stringent constraint on lithium content in the ZnO nanorods.\u003c/p\u003e"},{"header":"Declarations","content":"\u003ch2\u003eCompeting Interests Statement\u003c/h2\u003e\n\u003cp\u003eThe authors declare no competing interests.\u003c/p\u003e\n\u003ch2\u003eFunding\u003c/h2\u003e\n\u003cp\u003eThis work was funded by the project \u0026ldquo;DeteZnOs: Budget-friendly and sustainable-by-design UV-VIS photodetectors using chemically-produced ZnO nanostructures\u0026rdquo; in the framework of H.F.R.I call \u0026ldquo;3rd Call for H.F.R.I.\u0026rsquo;s Research Projects to Support Faculty Members \u0026amp; Researchers\u0026rdquo; (H.F.R.I. Project Number: 24835).\u003c/p\u003e\n\u003ch2\u003eAuthor Contribution\u003c/h2\u003e\n\u003cp\u003eG.P.P. performed the sample fabrication, XRD and SEM measurements, and data analysis. Z.S. and D.D.C. carried out ToF-ERDA measurements. A.Z., E.T., and A.L. performed the PIGE and ToF-ERDA measurements and contributed to data analysis. Y.G.L. conducted the chemical analysis and contributed to the manuscript results discussion and revision. C.D. contributed to the result interpretation as well as the manuscript revision. A.T. supervised the study, secured funding, and contributed to the original manuscript draft. E.M. conceived and supervised the study, developed the methodology, analyzed and interpreted the data, and wrote the original and final drafts. All authors discussed the results and approved the final manuscript.\u003c/p\u003e\n\u003ch2\u003eAcknowledgement\u003c/h2\u003e\n\u003cp\u003eWe would like to thank Dr V. Psycharis, Director of Research at INN, NCSR \u0026ldquo;Demokritos\u0026rdquo; for his assistance in receiving the XRD spectra as well as Dr G. Papageoergiou, Scientific Functional Researcher at INN, NCSR \u0026ldquo;Demokritos\u0026rdquo; with his assistance in the SEM imaging.\u003c/p\u003e\n\u003ch2\u003eData Availability\u003c/h2\u003e\n\u003cp\u003eThe data that support the findings of this study are available from the corresponding author upon reasonable request.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eMorko\u0026ccedil;, H. \u0026amp; \u0026Ouml;zg\u0026uuml;r, \u0026Uuml;. \u003cem\u003eZinc oxide: fundamentals, materials and device technology\u003c/em\u003e (Wiley-VCH, 2009).\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eFeng, Z. C. \u003cem\u003eHandbook of zinc oxide and related materials\u003c/em\u003e (CRC, 2012).\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eTashiro, A., Adachi, Y. \u0026amp; Uchino, T. Excitonic processes and lasing in ZnO thin films and micro/nanostructures. \u003cem\u003eJ. Appl. 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Controlled synthesis of periodic arrays of ZnO nanostructures combining e-beam lithography and solution-based processes leveraged by micro X-ray fluorescence spectroscopy. \u003cem\u003eMicro Nano Eng.\u003c/em\u003e \u003cb\u003e8\u003c/b\u003e, 100063. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1016/j.mne.2020.100063\u003c/span\u003e\u003cspan address=\"10.1016/j.mne.2020.100063\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e (2020).\u003c/span\u003e\u003c/li\u003e\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":true,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"scientific-reports","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"scirep","sideBox":"Learn more about [Scientific Reports](http://www.nature.com/srep/)","snPcode":"","submissionUrl":"","title":"Scientific Reports","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"stoa","reportingPortfolio":"Scientific Reports","inReviewEnabled":true,"inReviewRevisionsEnabled":true},"keywords":"ZnO nanorods, Li-doping, aqueous chemical bath deposition, PIGE, ToF-ERDA, point defects, p-type doping","lastPublishedDoi":"10.21203/rs.3.rs-8681116/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-8681116/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eAchieving reliable p-type conductivity in zinc oxide (ZnO) remains a long-standing challenge, with lithium frequently proposed as a candidate acceptor dopant in solution-grown ZnO. Despite numerous reports of Li-related electrical and optical effects, direct and element-specific verification of lithium incorporation in aqueous chemical bath deposited (CBD) ZnO has remained elusive. Here, complementary nuclear ion-beam techniques, Particle-Induced Gamma-ray Emission (PIGE) and Time-of-Flight Elastic Recoil Detection Analysis (ToF-ERDA), were employed to directly probe lithium incorporation in aqueous CBD-grown ZnO nanorods synthesized over a wide range of precursor concentrations. In all samples, no lithium was detected within the experimental sensitivity of either technique, establishing an upper bound for Li incorporation below 0.01 at.%. This unambiguous absence of lithium demonstrates that Li⁺ does not act as a substitutional or interstitial dopant under aqueous CBD conditions. The results are consistent with lithium influencing the growth chemistry and defect landscape of ZnO without lattice incorporation, offering a rational explanation for Li-related effects reported in solution-grown systems. More broadly, this work clarifies the role of lithium in aqueous CBD-grown ZnO nanostructures and underscores the value of nuclear spectroscopic methods for validating light-element incorporation in oxide semiconductors.\u003c/p\u003e","manuscriptTitle":"Direct Nuclear Spectroscopic Evidence against Lithium Incorporation in Aqueous Chemical Bath Deposition-Grown ZnO Nanorods","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2026-02-03 19:24:32","doi":"10.21203/rs.3.rs-8681116/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Revision requested","date":"2026-02-16T09:08:38+00:00","index":"","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2026-02-16T06:05:36+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"82580219717196629760437317632544907610","date":"2026-02-16T05:59:38+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2026-02-12T06:32:59+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"320354081504156924590557289055096201171","date":"2026-02-02T07:04:55+00:00","index":"hide","fulltext":""},{"type":"reviewersInvited","content":"","date":"2026-01-30T15:02:51+00:00","index":"","fulltext":""},{"type":"editorInvited","content":"","date":"2026-01-29T12:26:20+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2026-01-27T13:37:55+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2026-01-27T13:31:16+00:00","index":"","fulltext":""},{"type":"submitted","content":"Scientific Reports","date":"2026-01-23T16:08:04+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"scientific-reports","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"scirep","sideBox":"Learn more about [Scientific Reports](http://www.nature.com/srep/)","snPcode":"","submissionUrl":"","title":"Scientific Reports","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"stoa","reportingPortfolio":"Scientific Reports","inReviewEnabled":true,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"67f756d2-ab97-4e90-888b-724653844aff","owner":[],"postedDate":"February 3rd, 2026","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"published-in-journal","subjectAreas":[{"id":62134876,"name":"Physical sciences/Chemistry"},{"id":62134877,"name":"Physical sciences/Materials science"},{"id":62134878,"name":"Physical sciences/Nanoscience and technology"}],"tags":[],"updatedAt":"2026-03-09T16:04:15+00:00","versionOfRecord":{"articleIdentity":"rs-8681116","link":"https://doi.org/10.1038/s41598-026-43258-5","journal":{"identity":"scientific-reports","isVorOnly":false,"title":"Scientific Reports"},"publishedOn":"2026-03-05 15:58:00","publishedOnDateReadable":"March 5th, 2026"},"versionCreatedAt":"2026-02-03 19:24:32","video":"","vorDoi":"10.1038/s41598-026-43258-5","vorDoiUrl":"https://doi.org/10.1038/s41598-026-43258-5","workflowStages":[]},"version":"v1","identity":"rs-8681116","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-8681116","identity":"rs-8681116","version":["v1"]},"buildId":"XKTyCvWXoU3ODBz1xrDgd","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}